Research of microstructure and mechanical behavior on duplex (α + β) Ti-4.8Al-2.5Mo-1.4V alloy

The microstructure and mechanical behavior of the duplex Ti-4.8Al-2.5Mo-1.4V (Ti14) alloy were investigated by means of optical microscopy, electron microscopy, experimental model analysis, and hardness and tensile testing. During heat-treatment at between 600 and 1000 °C, the phase transformation sequence was found to be (α + β) → (α + β + α′) → (α′ + α″ + residual β). The (α′ + α″ + residual β) structure exhibited the maximum yield strength (σy = 920 MPa), hardness (HRC 36), and damping coefficient (188.3 × 10-4). However, the (α + β) structure achieved the greatest elongation (∼15%). It is believed that the lath-like α′ martensite not only increases the tensile strength, but also enhances the hardness of the Ti14 alloy. Moreover, it also plays a crucial role in increasing the damping capacity of the Ti14 alloy.